Communication systems include a transmitter and a receiver that communicate information over a link that carries the information. The link may be wireless (e.g., electromagnetic radiation (such as radio frequency), electro-optical signals, infrared signals, etc.), or physical (e.g., ADSL, power line communications, fiber optic signals, etc.). In a wireless communication system, the transmitter may be a mobile device and the receiver may be a base station or a cellular tower, and vice versa. Also, the transmitter and the receiver may be the same, for example, they both may be mobile devices or base stations. The base station may be positioned on a moving vehicle such as an aircraft, airship, blimp, spaceship or satellite. Generally, the transmitter sends a communication frame or data packet to the receiver on a single channel. Hence, each communication frame is serialized over a single channel. Each channel corresponds to a particular frequency. Present communication systems are configured to carry the information on a single channel at a time.
Frequency hopping is a technique that allows the wireless communication system to transfer data using multiple channels. In particular, frequency hopping allows the transmitter and the receiver to simultaneously “hop” to a single available channel to transmit and receive the data. The purpose of frequency hopping is to allow multiple devices to share a channel for the communication of information. Frequency hopping also allows the wireless communication system to scramble the data by serially transmitting and receiving communications using multiple channels. For example, a first channel can be used to transmit a first communication frame, a second channel can be used to transmit a second communication frame and so on. In frequency hopping systems, the channel or frequency of transmission may change at predetermined time intervals or in a pseudorandom manner. For example, the receiver may contain an algorithm that changes to the next frequency at essentially the same time as the transmitter without receiving successive frequency change information from the transmitter. Alternatively, the transmitter may include a pseudorandom number generator for generating a pattern of numbers that change the carrier frequency. The pattern of numbers is predictable from a relatively small set of defined values that are communicated to or predetermined within the receiver. The transmitter and the receiver are capable of operating in a number of frequencies and in a number of frequency bands, making use of spread-spectrum and narrowband communication techniques.
One drawback of conventional wireless communication systems is the difficulty in achieving high data transfer rates. This is partly because conventional wireless communication systems send data serially along a single channel. For example, the transmitter may send a byte or frame of data in a serial manner on a single channel to the receiver. Thereafter, the transmitter may send another byte or frame of data in a serial manner on another channel to the receiver. The transfer rates are limited because the receiver generally receives only one bit, byte or frame of information at a time. Some methods of achieving high data transfer rates include increasing the compression rate and increasing the frequency of transmission. These methods, however, still provide limitations as to the speed at which the data can be transmitted serially.
Another drawback of conventional wireless communication systems is the difficulty in correcting multiple bit errors at the receiver. When data is transmitted, errors in the data may occur from channel interference, drops in signal strength, loss in transmission, as well as other factors. These errors may be corrected using an error correction technique, such as cyclic redundancy check (CRC), which places a CRC packet at the end of the entire data packet. However, before any errors in the data packet can be identified, the entire data packet, including the CRC packet, must be received by the receiver. Once the entire data packet is received, the receiver can correct errors in the data packet but cannot correct errors in the CRC packet. Hence, any errors identified in the CRC packet requires retransmission of the entire data packet, including the CRC packet.
Thus, it should be appreciated that there is a need for a wireless communication system that achieves high data transfer rates and provides error correction of the CRC packet without retransmission of the data. The invention fulfills this need as well as others.